Process for forming a fibrous rubber base



Patented Mar. 5, 1946 simens e ASerial No. 4542922 v'fClaim. (c1.www1-sz) ffhisffmventionrelates :to aunethcd ofarecn'nditiorringxml'eanized irbber fiberwasteitoriorming a brous rubber*.basemateril. y The 'primary-object luf therinvention eisztoiproxide neconomicalrprocess lfor"fmfming 'a ecom- 'blaer 'and-.liberV:rmm'po'sition )from tire carcasses fand "whereby `rworn out fandydiscarded integration of V-r-i'bber rstripped ftire carcasses (known`thefar-t @as carcass-stock) vanctheir ing-,agentsfsuch fasipcwderedsulphur.

reduction to anely Aecm-rninuted statewhereby the curedrubber.constituentwillabe vreduced Ito a pulvenulentrorm and -tt1eeel-l11lcsic ber content will yJoe reduced, to 'av-substantially powdered-or oceulent state, and Ithen Aplastic-izing` the mass and effect-ingdevu-lcanization--of thecuredrubber cententsolely -by addi-tion to the`:poWderf-:d mass by vintergrinding therewith of a suitable rubbersefftenerfollewed :by the employment of heat and pressure .-toproduce asof-t fpastey mass .oi rubber containing-the undegenerated brousr.I-rlattgari-al of thefdisintegrated tire fearcasses, which-mass cantion wf' raw frubberffexten'ders, fillers etc.,and which ,maybemilcanizedby the'aase-oi vulcaniz- 'bemoldedfsheetei etc. withcr-Without the addi- :In "carrying the zprocess fa-br c -reinforeedrubber tire carcasses to befemployedlin the .pro 'ductiono theVproductare first stripped of '-all; or nearlyall, superimposed curedrubber -constitut lingf'tlietread and side wall Iportions, thusproducing the desired vcarcass stock; -fthe superimposed:curednrubberIbeing removed lfrom lthe fabric core -of thecarcasslbyburlngwhich-reduces such cured :rubber to `a1-r`1ne1ydivided orcomminuted state.

Iheresultant powdered cured; rubber may be freclaimed in -e(mventional:fashion to 'produce fthe ordinary .reclaimed frubberof commerce,v @butwhich Y`in its -rd-ry v.pvul'verulen't state may 'bel mixed ire-reveilkffe'wn ternes@ Awith the material :reclaimed in 'the vffl-iereinafterNdescribed process.

f Ihe strippedabricporticnof the tire `carcass furca'rcass stock, :whichA'comprises a mass of tlbrous fcordfs 'embedded in irubben first reducedvto f a fcoarse Ygranular estate fby passing n-tl'rr'eugh .afsuitablemill inra fdryrstateresulting in a mass con`Asistirrg'Infisnra'll .drychunksfabout the size of peas fandwhichfchunks :are com'posed of :short y-lexigths offabric fibers bound.in :cured rubber. The dry ffgramilar massthus obtained iis thensubjected to fsa refining action, -whichfeonsists in grinding thet:small'chfunks inia' dry statetofreduce thematerial itc a.lpills/emi'ent ver :oc'cuient form therebyvprofducing "a, fine dryfpwder oroccomposedaof #fine particles fef fcured :rubber vand rfi-nepar-ticles and :minute lengths-of fiber. f

mie rubber 'fand 'ber .powder fis g-then Antergrourid "with fa volume of*La liquid rubberl softener wdf only f'sufcient `c mantity @inproportion to the -drfy 'particles fof the powderthat t'vlren eachf'Palticle f the irriass :absorbs itsfquota. of-.the softener it willremain in its generalgranular form-rhutwll bef-slig'htly'n-iisterred'such .that under slightpressure the particles will adhere together inchunk or cake-like form.

A proportion of approximately 20% of the liquid softener by weight tothe powdered mass under treatment has been found in some instances toproduce a satisfactory result, but such proportion is not critical andis subject to considerable variation; the amount of softener used inproportion to a given quantity of the powdered cured rubber and fiberbeing varied according to the quality of the powder as to the life ofthe cured rubber constituent, and as to the proportion of extenders,fillers, sulphur, and other foreign materials as may be incorporated inthe carcass stock during the initial manufacture thereof. The proportionof the softener may also be varied according to the kind and quality ofthe fibrous base product desired. For example, I have found that in someinstances less than of the sofs tener by weight of the powdered masswill be adequate while in another instance as much as of the softenerwas required. In any case, the proportion of softener employed to anygiven quantity of the powder will be sufficient to be absorbed by thecured rubber yconstituent and to effect devulcanization thereof and atthe same time effect moistening of the fiber constituent.

The intergrinding of the powder and the sofv tener is preferablyeffected at a temperature of about 200 F. or at some temperatureslightly below boiling, and for such length of time as to insurethorough impregnation of the powder with the softener. The statedtemperature at which the intergrinding is effected is Subject tovariation and is not critical, it only being essential that atemperature sufficiently high to effect destruc tion of the fine fibersor decomposition of the mass be not used and yet be'sufficiently high toinsure thorough impregnation of the rubber particles by the softener.

While this intergrinding of the rubber-fiber powder with the liquidsoftener may be effected in any suitable manner and by any suitablemeans, the employment of a mixing mill equipped with friction rollersrunning in sliding contact with each other in opposite directions but atdifferent speeds, is preferable. In the operation of a. mixing mill ofthis character, the rollers become heated by friction generated byreason of .their relative movement Vin sliding contact with each other,and accordingly the mill is run idle for a sufficient length of time tobring the rollers to a desired temperature before feeding the materialthereto. On the rollers being thus heated vto a requisite temperature ameasured batch of the rubber-fiber powder in a warmed condition,preferably freshly ground and heated by the action of friction in thepulverizing operation, is fed to the friction rollers together with ameasured quantity of the liquid softener which latter is pcured into thepowdered mass While in a heated condition at a temperature slightly lessthan boiling. In heating the softener it is placed in a kettle fittedwith a steam coil and is there brought to the desired temperature alittle less than boiling, which renders the softener very thin so thatwhen it is ground hot into the rubberber powder in the mill the liquidand powder will be readily intermixed. However, in order to insurethorough dispersion of the oil throughout the mass of powder particles,the mass is repeatedly run through the mill as many times as occasionmay require and as may be determined y necessary by the operator.

The treatment above recited results in a mass of loose, granular butmoist particles of rubber and fiber which can be formed in chunks orcakes on being subjected to light pressure.

The liquid softener used may be of the oils or tars commonly employed asrubber softeners and in the production of rubber-like substancesincluding, for example, vegetable oils such as cotton-seed oil, linseedoil, rape-seed oil, soy-bean oil, castor oil, sesame oil, corn oil, andthe like; or animal oil such as whale oil, fish oil, cod-liver oil andthe like; or a mineral oil such as crude petroleum, or a number of itsdistillates, or common road-oil thinned with distillate; or tars derivedfrom the distillation of wood or peat. Either an oil or tar may be used,or a mixture of oil and tar may be employed. I have found in practicethat the' use of pine-tar alone as a softening agent gives highlysatisfactory results, and' because of this and its availability and lowcost as well as the facility with which it can be handled and appliedand the better quality of product obtained, is preferable to the othersofteners mentioned.

I am aware that'oils and/0r tars have been heretofore commonly employedas rubber softeners and devulcanizing agents and accordingly I do notclaim such use as being my invention; my

process embodying the use of such materials for,

the purpose to which they arerordinarily put in reconditioningvulcanized rubber, but in a new fashion and such as to preserve nelycomminuted fabric particles incorporated in and with the cured rubberbeing devulcanized.

The granular softener impregnated particles of rubber and fiber-withoutthe addition of other substances are then arranged on a suitable trayand slightly compressed to form a layer of approximately three or fourinches inthickness.

, The mass is then subjected to the action ofheat and pressure such asin saturated steam under a pressure of approximately` pounds for aperiod kof about four hours whereby the materials are cooked at atemperature of about 338 F. and are thereby converted into ahomogeneous, soft, spongy, pliable mass. This coo-king operation iseffected in a. suitable autoclave. The spongy mass thus obtained is thenrolled into a thin sheet or ribbon having a wafer-like thicknessapproximating that of a sheet of tissue paper or writing paper, whichribbon is then wound on a drum until the overlying layers acquire athickness of one inch or thereabout, whereupon the resultant cyl, index`of layers Vis out lengthwise and removed from the drum and flattened outto form a sheet or slab constituting the finished product; ,thesuperimposed layers of the wafer-like ribbon adhering together undertheir inherent cohesivenessand forming a homogeneous pliable body `atnormal atmospheric or room temperatures. 'I'his rolling of the mass intothin sheets and assembling the sheets in a slab insures thoroughdistribution of the rubber and fiber particles throughout the slab andthereby results in a uniform product.

The product resulting from the foregoing process constitutes a basematerial comprising a .ployed with or Without the addition of cruderubber, or extenders such as factice, or reclaimed rubber, and may beadmixed with clay, accelerators, nonoxydizing agents, etc. according tothe character of the manufactured product desired. The base material isespecially suitable for use `in forming floor coverings, shingles, andthe like,

manufacture of rubber heels and soles for shoes.

It may be converted into hard slabs by addition of clay, diatomaceousearth, and other hardening substances. It may be rolled into ilexiblesheets. agents, coloring materials, and petroleum tar.

Various other substances may be incorporated therein such as cork,sawdust, and the like. The

It may be mixed with nonoxydizing' powdered cured rubber obtained fromthe treads and side walls of the tire carcasses is admirably suited foruse with the base material without further treatment, and may bevulcanized in the mass with the addition of sulphur. The base materialmay be used in its natural state for insulation purposes especiallywhere interposed between walls. It may be cured or semi-cured bysubjecting it to the action of heat. It may also be employed as acushioning material. In fact the product is subject to a wide range ofuses and various treatments comparable to that of reclaimed rubber withthe advantage, however, of being superior to reclaimed rubber in manyinstances by reason of its brous or felted character. y

An important and the essential feature of this invention is theretention in the product of the brous content of the carcass stocksubjected to treatment in a completely undegenerated state, which isaccomplished by eliminating in the processing of the stock the use ofany ber destroying or cellulose deteriorating substances such as causticalkali; the retained fibers serving to increase resistance to wear andresistance to oxidation of articles manufactured from thev product.

This application is a continuation of an application Serial Number413,980 iiled by me under date of October '7, 1941.

vI claim:

.The process which consists in reducing the rubber bound fabric of tirecarcass stock to a flocculent state, intergrinding with the resultantpowder a quantity of pine-tar while heating the mass to a temperature'slightly less than boiling, the quantity of pine-tar'being proportionedto the quantity of powder such that when interground therewith thepowder will remain in moist granular form, forming the resultant mass ofmoist granules into a slightly compressed layer, and cooking the layerin steam at a temperature of about 338 F. and under a pressure of about100 pounds for about four hours.

GROVER C. BERRYMAN.

